Plasma enhanced substrate process chambers are widely used in the manufacture of integrated devices. In some plasma enhanced substrate process chambers, multiple radio frequency (RF) generators are utilized to form and control the plasma. Each generator is connected to the substrate process chamber through a matching network. For processes using high frequencies (HF), matching networks commonly use lumped elements, such as commercially available capacitors.
However, for processes using VHF frequencies higher than 100 MHz, conventional lumped elements, such as capacitors, are impractical because the value of such components are not easily realizable. At these frequencies, distributed elements based on transmission lines are typically used. However, the RF transmission line is long at these frequencies and devices based on the full wavelength or quarter wavelength are, therefore, also large. In addition, these matching networks are traditionally fixed and the reflected power is absorbed in non-reciprocal devices like circulators and isolators.
Therefore, a need exists for an improved apparatus for VHF match tuning.